Chrome OS OOBE: Fix Authenticator variable names

This CL renames variables that have obsolete names like "gaiaAuthHost",
now that the "GaiaAuthHost" class doesn't exist anymore and is finally
renamed to "Authenticator" everywhere (see crrev.com/c/1605919).

Also fixes some comments that were referring to the old "auth host"
thing.

This is a pure refactoring CL, no functional changes are expected.

Bug: 470893
Test: existing tests
Change-Id: Ia07803527e0bf9148e021266cb2e2bc9a1fa67ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617832
Reviewed-by: Denis Kuznetsov <antrim@chromium.org>
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661360}
5 files changed